Why do we rotate the wrist at the end of middle inner forearm block? I know it helps with power but how/why?
A block may be used to deflect or stop an attack, and, when used to stop an attack, the block may also be used as a counterattack. A defecting block simply pushes and redirects the attack away from its intended target. To stop an attack, the block gets between the attack and the target and takes the blow instead of a letting the blow strike its target. To use a block as a counterattack, the block must not only deflect or stop the attack; it must also damage the attacking body part.
When using the inner forearm block, you are actually turning the body to avoid the attack and using the block as an additional measure to prevent the attack from reaching its target. The block may simply deflect the attack with a push, or it may use the power in the upper arm and shoulder to intercept and stop the attack. When stopping the attack, the forearm must absorb all the energy of the attack, which means it is being struck by the attack. This can hurt and may do damage to the forearm, especially if the block is against a shin during a roundhouse kick attack.
When something small and light is struck by something larger and more massive, the smaller object usually receives the most damage. To counter this, the smaller object must be moving a greater velocity than the larger object. The problem with the inner forearm block is that the upper arm and shoulder move relatively slowly. To increase the velocity and thus increase the striking force of the forearm, we must quickly rotate and snap the forearm into the attacking object. The striking side of the forearm is now moving a much greater velocity than without the rotation. The snap also help us to focus the power of the block into a single point in space instead of applying the force equally throughout the block’s movement. Now, instead of being struck, the forearm is doing the striking.
Have you ever saw two people accidently bump heads while playing? It causes pain in both people, but usually one is in tremendous pain while the other is simply rubbing a sore spot. The difference is in which head did the striking and which was struck. Usually, the two heads do not strike each other equally, one is moving faster and than the other so it is the one that strikes the other head. The striking head usually receives less damage. When executing the inner forearm block, if you snap rotate the forearm, tense the entire body at impact, and rotate the mass of the body into the strike, the attacking limb will receive the most damage.
I started my martial arts training in old-school Okinawan karate where we practiced blocking where you and your opponent did identical full-power blocks against each others arms. In the beginning, you went home with both sides of your forearms red and bruised, but after a few weeks, they toughened and became weapons. Because of this early training, during years in Taekwondo I have been criticized by instructors for blocking too hard and hurting opponents. I always questioned how I could be hurting them since I was not attacking. My attacks were always precise and focused, so they did no damage. When my opponents attacked, I blocked to prevent the attacks from striking. If it hurt the attackers, it was because they were using a powerful attack. It they wanted to avoid the pain, all they had to do was not attack, or use weaker attacks. My hard blocks made opponents reconsider their attacks. I have always told students that you can win a fight without ever attacking the opponent if you use powerful, hard blocks.